NO115087B - - Google Patents

Description

Process for the production of cleaning agent preparations.

This invention relates to new methods for the production of detergent preparations containing hydrated alkali metal phosphates. More particularly, it relates to new methods by which cleaning agent preparations with low mass density containing at least one hydrated polyphosphate can be produced without spray drying.

The invention provides a method for the preparation of a cleaning agent composition which consists in keeping a dispersion with a continuous liquid aqueous phase and a dispersed phase "consisting of a substance which reacts with water to form a water-soluble alkali metal polyphosphate hydrate" at a temperature below 135°C for to enable reaction of said substance with the water in said aqueous phase; that at least part of this dispersion is converted into a foam; and while said part is in this foam state, a substantial part of said reaction is carried out, while it is removed sufficiently freely water from said continuous water phase, whereby a solid, porous product containing said alkali metal polyphosphate hydrate is formed.

Until now, it has been considered necessary, when a cleaning agent manufacturer wanted to make a cleaning agent preparation with a relatively low specific gravity (i.e. less than 0.8), that he either had to use raw materials with a very low specific gravity, or use the process that is known as spray drying at least in one step of the entire manufacturing process. But spray drying is a relatively expensive process, which first of all requires a considerable capital investment in the spray drying equipment (which, for example, includes such things as high-pressure pumps, a very large "spray tower", and various equipment for heating and regulating the air flow to " the tower"). Also, the cost of the heat actually needed for the spray drying (to evaporate water from the slurries) is high, compared to the overall cost of raw materials for the final product with a low specific gravity. As a result of the high price for spray drying, many of the smaller cleaning agent manufacturers have not found themselves in a position to spray dry their products, and as a result they are competitively placed in an unfortunate position, because many consumers of cleaning agent products prefer to use the lighter products ( with low specific gravity).

The preferred polyphosphate used in most detergent products at present is a tripolyphosphate, and in particular sodium tripolyphosphate. But tripolyphosphates have a definite shortcoming which at present (in normal practice for cleaning agent production) can only be partially overcome, and this only by implementing very precise precautions during the usual manufacturing steps. This deficiency is a consequence of tripolyphosphate's propensity for hydrolytic breakdown. During the time when a slurry is formed and this is finally spray-dried, generally a significant part of the tripolyphosphate is hydrolysed to orthophosphates and pyrophosphates which are not nearly as effective (as complex formers) in building up the detergent products as tripolyphosphate. These are therefore not nearly as desirable as tripolyphosphate in the final detergent products.

Moreover, it is generally preferred that before a cleaning agent slurry is spray-dried, at least most of the sodium tripolyphosphate it contains should be hydrated. But when a slurry containing hydrated tripolyphosphate is spray-dried, a significant part of the tripolyphosphate hydrate breaks down (probably because of the high temperature the slurry must be subjected to if it is to be spray-dried effectively), and acidic decomposition products appear which are not nearly is as desirable in the final detergent products as the tripolyphosphate is.

It is therefore a first object of the present invention to provide methods by which cleaning agent preparations containing hydrated alkali metal polyphosphates and which have a relatively low specific weight can be produced without the need for spray drying.

Another object of the invention is to provide methods by which cleaning agent compositions with relatively low specific gravity can be produced and which contain hydrated alkali metal tripolyphosphates, especially sodium tripolyphosphate hexahydrate, without exposing the hydrated salts to excessively high decomposing temperatures.

Another object of the invention is to provide methods by which cleaning agent compositions with widely different physical properties can be made (including such as very different specific gravity, particulate solids, and shaped solids containing cellular structure, in addition to shaped solids containing compressed particulate solids ), using practically the same basic equipment for the production of each type of composition.

The above as well as other objects of the invention which will appear from the following description can be achieved according to this invention by using selected process conditions and raw materials which will lead to (a) formation of foam in a detergent slurry, (b) hydration of a substantial portion of a suitable alkali metal polyphosphate salt, while the slurry is in a foam state, and (c) that sufficient water is removed from the slurry, while this is in foam form, so that a solid (currently particulate) porous product is thereby formed.

The method according to the invention thus involves manufacturing. of a cleaning agent preparation containing a water-soluble alkali metal polyphosphate hydrate by preparing a dispersion of a condensed phosphate starting material in water in the presence of a foaming agent, and the dispersion is brought to a foamed state, and the peculiarity of the method is that a condensed phosphate starting material comprising alkali metal trimetaphosphate is dispersed in water, the dispersion also contains at least approx. half of the stoichiometric amount of a strong base required to convert the alkali metal trimetaphosphate, preferably sodium trimetaphosphate, to tripolyphosphate and at least 5 moles of water per moles of said trimetaphosphate and said dispersion are kept in a foamed state at a temperature in the range of 50 to 135° C, preferably 80 to 120° C, during which said trimetaphosphate reacts with said base and said water so that a hydrated tripolyphosphate is formed and the reaction mixture hardens to a slightly porous solid..

It is particularly advantageous to use a total amount of material in the dispersion that constitutes at least 10% by weight of the total solids in the dispersion, and further, the dispersion should suitably from the beginning contain at least 10% by weight of sodium trimetaphosphate and at least 0.5% by weight of sodium sulfate.

The methods for producing light detergent compositions with low specific gravity in accordance with the invention require the use of a "slurry" to achieve several special advantages, including achieving a better uniformity in the final products. Cleaning agent "slurries" are well known in the art and they do not need to be described in detail here, except to point out that the slurries that can be used for methods according to this invention must at least contain enough water to hydrate all the alkali metal polyphosphate in the finished cleaning agent preparations, which can be made from them, and in addition sufficient water so that the slurry initially has liquid properties. Usable slurries should thus contain at least 10 percent by weight of water in relation to the total weight of the finished slurry. For some of the preferred designs of the invention, it is preferred that the slurries from the beginning contain at least 25 percent by weight of water. Because in most of the methods according to the invention it will be necessary to evaporate at least part of the water found in the slurries (especially when the amount exceeds that necessary for hydration of the polyphosphate salt), some of the advantages accruing to those who carry out the invention are most prominent when slurries containing no more than 50% water by weight are used.

Thus, one has unexpectedly found e.g. that if hydration of one of the suitable polyphosphate salts (to be described in detail later) is effected during the time when one of the preceding slurries is in a foam state, so that sufficient "free" water is removed from the slurry to cause thickening and finally "solidification" (transition to solid phase) of the slurry, then this will lead to particulate solid and/or shaped products with unexpectedly low specific gravities. The term "free water" shall here denote the water that was originally present in the slurry and that is present in the composition in question as present in an unbound, non-evaporated state (i.e. not present as a hydrate of any of the salts in the composition). It should be noted that the use of the term "free" water with reference to a given composition at a given time does not necessarily mean that the composition referred to is in a liquid or even semi-liquid state, since many apparently solid detergent compositions can contain as much as ten percent by weight " free" water or more without losing most of their solid properties.

It is an advantage of the present invention that practically any water-soluble and "hydratable" alkali metal polyphosphate salt, i.e. which can be hydrated in an aqueous slurry, can be used for the production of cleaning agent preparations according to the invention. Since cleaning agent preparations are generally intended for or formulated for use in the area of so-called "hard" water (i.e. water containing dissolved "hardness" ions such as calcium, magnesium and iron which can react, for example, with soap to form a insoluble, unwanted product), then it is preferred that the hydratable alkali metal polyphosphate salt be one that has the ability to complex these "hardness" ions when dissolved in "hard" water in sufficient quantity. Alkali metal polyphosphates known to have this particular property include alkali metal tripolyphosphates, alkali metal pyrophosphates, and alkali metal chain polyphosphates having from 4 to 8 or more phosphorus atoms in their molecules. Particularly preferred within this group are the alkali metal tripolyphosphates, and among them again especially the sodium tripolyphosphates. These polyphosphates having sodium or potassium cations are generally a preferred class for use in the methods of this invention, largely because of the economic advantages they have over the other hydratable alkali metal polyphosphate salts described above.

The detergent preparations with low specific gravity which can be made by methods according to this invention are those which contain a significant amount of hydratable alkali metal polyphosphate, i.e. usually at least 10 percent by weight and often as much as 75 percent by weight in relation to the total weight of the final solid detergent composition. But in general it is preferred that the final preparations should contain between 15 and 60 percent by weight of alkali metal polyphosphate salt, of which at least 60 percent, and preferably at least 75 percent by weight, is in a hydrated state.

Although it was emphasized in connection with the above purposes that the hydrated polyphosphate salts in the method according to the invention do not need to be exposed to such high, degrading temperatures as those normally used in spray drying processes for cleaning agents, it will nevertheless generally be necessary applying heat in some way to the detergent slurries used herein to obtain temperatures in the slurries of at least 50° C, during some of the later steps of the present processes. A method has been discovered by which both heat and the desirable tripolyphosphate can be introduced into the cleaning agent processes according to the invention at the same time, and by which several other advantages can also be achieved (including greater ease in controlling the viscosity of the cleaning agent slurries than is usual possible using common slurry processes that include the use of tripolyphosphates and a faster overall manufacturing process compared to common processes for manufacturing comparable detergent products and others). This method consists in using an alkali metal trimetaphosphate, and preferably sodium trimetaphosphate, as one of the most important raw materials in the cleaning agent slurry. Accordingly, such processes which include the use of alkali metal trimetaphosphates constitute particularly preferred embodiments of the invention. These preferred designs enable a detergent manufacturer to take advantage of the use of the reaction of alkali metal trimetaphosphates with a base in the presence of alkali metal cations (if a substantially completely water soluble final detergent composition is desired) to produce an alkali metal tripolyphosphate. The reaction, which is accompanied by a large evolution of heat, is believed to be represented by the following series of steps:

Initially, the trimetaphosphatrine is cleaved by the base, and the tripolyphosphate ion is formed, as shown in equation (1):

The tripolyphosphate in the slurry then crystallizes as hydrate, as shown in equation (2):

where M is an alkali metal cation and y is an integer equal to the number of water molecules necessary to form an identifiable hydrate salt of the particular alkali metal tripolyphosphate resulting from the reaction described above. In general, y will be an integer in the range of 1 to 15. For the reasons stated above, it is preferred that M represents sodium, and that therefore y is equal to 6.

If an alkali metal trimetaphosphate, and in particular sodium trimetaphosphate, is used for the composition and production of cleaning agent compositions in accordance with the invention, then practically any amount of the substance can be used up to 60% by weight, in relation to the total weight of the finished cleaning agent, or even more . But the amount of alkali metal trimetaphosphate to be used depends in reality on two requirements from the detergent manufacturer's side, namely the amount of tripolyphosphate he wants in his final detergent product, and the part of this tripolyphosphate that must be present in a hydrated state. Since the products resulting from the implementation of this invention should generally contain at least 15% by weight of hydrated tripolyphosphate (when trimetaphosphate is used as a raw material), the slurries referred to here will ordinarily contain at least 5 to 8% by weight of one of the alkali metal trimetaphosphates to begin with (relative to the weight of "solids" in the slurry). On the other hand, due to the presence of a strong aqueous base and other cleaning agent components in the ready-made slurries, generally no more than 60% by weight of any of the alkali metal trimetaphosphates can be used, if relatively complete conversion of the trimetaphosphate to tripolyphosphate is desired during the preparation of the cleaning agent . It is preferred that the amount of alkali metal trimetaphosphate used in the aqueous slurries according to the invention should be from 15 to 60 percent by weight (in relation to the total weight of the finished slurry just before the "hydration" in the method according to the invention. This hydration will be described in more detail later. )

The bases which can be used in carrying out the invention are all those which can enable the formation of sufficient hydroxyl ions in the aqueous slurry to react with the alkali metal trimetaphosphate in accordance with the reaction outlined above. It has been found that in the group of substances known as "bases", only the relatively strong ones can cause the reaction of trimetaphosphate to tripolyphosphate. In the description and the claims, it is intended that the term "strong base" should include those bases which are strong enough to induce the formation of an "excess" of hydroxyl ions in aqueous solutions. media containing dissolved alkali metal tripolyphosphate. For the purposes of the invention, the "strong bases" that can be used are those which give a solution pH measured at 25° C of at least 10.2 when dissolved in distilled water at the level of 1% by weight. It will be understood that the term "strong base" will for example include such basic compounds as e.g. alkali metal carbonates, alkali metal silicates, tri-alkali metal orthophosphates, alkali metal and alkaline earth metal oxides, etc. 1. (which compounds do not actually contain hydroxyl ions, but produce hydroxyl ions (high pH) when dissolved in water, as well as some of the quaternary ammonium hydroxides , the alkali metal hydroxides and the alkaline earth metal hydroxides such as calcium hydroxide, magnesium hydroxide etc. Economic points of view will generally dictate that you use the "strong bases" which are inorganic. Among these, you prefer to use alkali metal hydroxides, carbonates and silicates (with SiO2/M20- ratio lower than 2.0, where M is an alkali metal cation.) Even more preferred are the sodium and potassium forms of these substances.

The amounts of the various strong bases described above, which can be used for this invention, can vary considerably, depending on such factors as the molecular weight of the base, its basic strength, the rate of dissolution in water, etc. But the amount must always be sufficient to provide sufficient hydroxyl ions so that at least a significant part or amount (ie at least one half and preferably seven tenths or more) of the alkali metal trimetaphosphate in the slurry can be converted to the corresponding alkali metal tripolyphosphate. Thus, the quantity of relevant inorganic base that can be used (in the slurry) when carrying out the invention will generally be at least sufficient to deliver approx. 1 and preferably 1.4 mole equivalents of hydroxyl ions per moles of trimetaphosphate present in the slurry. Because 2 moles of hydroxyl ions are required to convert one mole of trimetaphosphate to tripolyphosphate, it is further preferred that the slurry be composed so that it contains at least 2 mole equivalents of strong base per moles of trimetaphosphate present. Because very high concentrations of base in the cleaning agent slurries will in time cause the breakdown of tripolyphosphate (especially hydrated tripolyphosphate), and also because some of the excess base (the amount exceeding that required to convert the trimetaphosphate) must ordinarily be neutralized with acid before the "drying step" in the process when a very large base excess is used (ie to maintain a desirable alkalinity in the final detergent product), then the amount of strong base found in the detergent slurries when carrying out the invention will generally not be greater than 10 molar equivalents , and preferably 6 molar equivalents of base per mol trimetafos barrels in the slurries. Further precautions that should generally be observed when such extremely strong bases as the alkali metal hydroxides, and especially sodium hydroxide, are used for the conversion of trimetaphosphate to tripolyphosphate, shall be discussed together with the mention of the various manipulative methods that can be used in carrying out the invention.

Although it is clear that some inorganic bases are commonly used in cleaning agent compositions and processes, the amounts of bases which concern this invention will, practically without exception, exceed the amounts currently used. For example two percent solutions of common spray-dried detergent compositions in distilled water often show certain alkaline pH values from 8 to 10.5 or perhaps even slightly higher than 10.5. One wants to keep these alkalinity values in the final product because the products often work better under slightly alkaline washing conditions. In addition to this, a certain degree of alkalinity is required in the product to keep the silicate corrosion inhibitors in a water-soluble form. However, the practice of the present invention generally requires that considerably larger amounts of base be introduced into the cleaning agent slurries than has been used up to now.

It is another advantage of the invention that when alkali metal trimetaphosphates are used as described above, convenient control of the rate of hydration of the resulting tripolyphosphate salt in the detergent slurry can be obtained. This is a clear advantage in relation to cleaning agent slurry processes of the former kind where sodium tripolyphosphate e.g. is the most commonly used polyphosphate raw material, because the hydration rate of sodium tripolyphosphate is normally a very difficult but important process variable to control. This easy control of the hydration rate further gives the advantage of great flexibility to the methods according to the invention. Some of the consequences of this special advantage will be discussed in more detail later. It is generally the case that the higher the temperature in the aqueous mixture of strong base and alkali metal trimetaphosphate, the greater the rate of formation of the alkali metal tripolyphosphate resulting from the alkaline conversion of trimetaphosphate described in equation 1 above. However, as long as the strong base is kept away from slurries containing alkali metal trimetaphosphate, very little, if any, conversion of trimetaphosphate to tripolyphosphate occurs no matter how high the temperature is maintained in the slurry.

The rate of conversion of trimetaphosphate to tripolyphosphate can be increased by increasing the ionic strength (concentration) of a given detergent slurry. Those who prefer to use very high conversion rates in processes according to the invention can therefore advantageously do this by using highly concentrated cleaning agent slurries. It has also been discovered that the presence of more than 0.5 weight percent sodium sulfate in the slurry (while the trimetaphosphate conversion reaction is taking place) somehow acts as a catalyst for the conversion reaction and in the meantime increases the conversion rate as much as 50% or more.

Because a given amount of alkali metal metaphosphate in a given cleaning agent slurry contributes significantly less to the slurry's apparent viscosity than a corresponding amount of sodium tripolyphosphate would (which is generally mostly found in the slurry as hexahydrate), it can e.g. slurries with unexpectedly low viscosities are created during the mixing step for the detergent processes. This low viscosity in the slurries results in significant savings in comparison with otherwise equivalent slurries containing hydrated or hydrating tripolyphosphates, in the total power consumption of the entire detergent process, and particularly in the mixing stage for such processes. On the other hand, one can handle more concentrated slurries (containing less water) in a given set of mixing or pumping apparatus, if desired, compared to equivalent tripolyphosphate hydrate containing slurries. Data reproduced in Table 1 below give some idea of how large this reduction in slurry viscosity can be when sodium trimetaphosphate (plus 2 moles of NaOH per mole of trimetaphosphate) is used in the preparation of detergent slurries, compared to a conventional method for producing an equivalent detergent slurry with sodium tripolyphosphate after the low-temperature modification.

In general, one does not need to think about how hot the detergent slurries containing the alkali metal trimetaphosphate should be kept while the strong base is away from the slurries. However, because of the very high rate of decomposition of hydrated tripolyphosphates (such as the preferred sodium tripolyphosphate hexahydrate) when temperatures are raised substantially above 115°C, the temperature of slurries containing alkali metal trimetaphosphate used in accordance with the invention should generally be kept below 135°C and preferably below 120° C, while the alkali metal trimetaphosphate is converted to tripolyphosphate. Similarly, since the rate of conversion of trimetaphosphate to tripolyphosphate with a strong base increases with increasing slurry temperature, slurry temperatures should generally be maintained above 50° C. and preferably above 70° C. at least during the last half of the conversion. But if desired, even lower temperatures than 50° C can be used. (Higher temperatures than 105° C can be obtained in slurries and reaction mixtures by carrying out the processes under pressure higher than atmospheric).

Even if fairly low slurry temperatures of around 70-80°C are used for a large part or even most of the time when the trimetaphosphate is converted to tripolyphosphate, it is clearly advantageous to allow the temperature to rise to the boiling point of the free water in the slurry during the last phase of the conversion reaction to thus convert some of the water in the slurry into steam. This steam, which is generally initially generated in the form of separate gas bubbles (steam) in the slurry, can in turn cause the slurry to be converted into a foam of relatively low density. When then the rest of the trimetaphosphate is converted into tripolyphosphate (while the slurry is in the form of foam), and the tripolyphosphate is rehydrated, the apparent viscosity in the slurry becomes higher and higher. After a substantial part of the free water in the slurry has either been absorbed by the tripolyphosphate to form the hydrated salt or has evaporated out of the slurry (or generally both), the reaction mixture becomes a solid, apparently "wet" mass which generally still contain several percentages by weight of free water. This can be removed, if desired, by subsequent drying of the wet mass, or by additional absorption of the free water via hydrate formation. It has been observed that such "delayed" hydrate formation can occur even after the conversion reaction described above. It can e.g. readily enter into compositions containing such hydratable substances as sodium sulfate, and certain of the phosphate salts form their hydrates at temperatures below those normally used during the above-described foam hydration step (described above) in the process according to the invention.

If the aforementioned foam hydration step is carried out under atmospheric pressure and the cleaning agent slurries only have water as the continuous phase, then it is usually necessary to heat the slurries to a temperature between 100°C and 105°C to provide steam via conversion of water to steam, as described above . Sometimes, if it is desired to carry out the foam hydration process at temperatures lower than 100-105° C, a certain amount of a relatively low-boiling organic liquid which is completely miscible with water, such as methanol, ethanol, isopropanol, acetone, dioxane, can be used o. 1. or combinations thereof, together with the water as liquid continuous phase in the preparation of the cleaning agent slurries as previously described.

It will be noted that in both of these embodiments the temperature of the reaction medium (the slurry which is subsequently converted into a solid detergent product during foam hydration) is kept high enough to form steam, either in the form of pure water vapor or as the low-boiling organic liquid/water zeotrope, for example, depending on the composition of the liquid continuous phase of the slurry, as it is the steam that produces the lightweight foam. But it is not absolutely necessary that the gas that forms the foam is steam. Indeed, it is sometimes advantageous in the practice of the invention to create the foam during the foam hydration process discussed above by blowing, dispersing or injecting a gas other than steam into the slurry. This applies in particular where lower slurry temperatures and conversion rates for the trimetaphosphate are desired. It can be done in any of several ways, which will be apparent from the description for anyone with a reasonable knowledge of the industry. The gas that is injected can be air, oxygen, carbon dioxide, nitrogen, nitrogen oxide, hydrogen, propane, methane, ethane, argon, neon, superheated steam etc. 1. It can also be any of a number of relatively lower boiling synthetic substances which are either gases at temperatures below 100° C and atmospheric pressure, or which can easily be converted into gases by relatively small adaptations of the temperature and/or pressure, such as e.g. the fluorinated hydrocarbons comprising CChF, CCI2F2, CCIF2CCIF20. 1.

When the conditions during the foam hydration step are such that the rate of hydration of the polyphosphate is relatively slow (as when the slurry temperature below about 70° C is used during the conversion of one of the alkali metal trimetaphosphates), then the reaction (hydration) mixture must generally be held in the foam state longer than when the conditions are such as to support a higher rate of hydration, provided most of the advantages obtainable by using the present invention are desired. This time period can be reduced (all other conditions being the same in any given process) by using a method which involves injecting a gas, the gas being heated before being introduced into the hydration mixture to a temperature high enough to remove some of the free water from the slurry via evaporation. Heat can also be supplied directly to the slurry with a conventional heat exchanger or through the walls of the mixing tube, belt or other container where the foam hydration had to be carried out.

Although several special methods have been outlined for producing the required foam from the cleaning agent slurries, it will appear from the description that other methods can be used to form the foam without thereby necessarily deviating significantly from the advantages that can arise from the use of the invention. All that is generally necessary in this respect (so far as the foam hydration step in these processes is concerned) to carry out the invention is that the slurry is transferred to foam, and that at least a substantial part of the hydration of the polyphosphate is carried out during the slurry has the form of foam. It is e.g. extremely difficult to obtain finished detergent products with a very low mass density by methods according to the invention if the maintenance of the foam in the slurry and at least part of (and preferably the later part of) the hydration of the "hydratable" polyphosphates are not carried out at the same time. In general, acceptable detergent products with lower densities can be obtained if as little as 5% by weight (or even less) of the total "hydratable" polyphosphate in the composition or slurry is hydrated' while the slurry is in the foam state, although it is preferred that at least 10% by weight of the hydration occurs during this foam hydration step among the processes of the invention.

It will be noted that during the foam hydration step, the foam may be generated continuously during the entire period, or during only part of the latter part of the period when the polyphosphate is being hydrated. Or sufficient foam can be created to begin with, and the reaction conditions can then be adapted and maintained so that at least a large part of the gas bubbles are retained in the slurry until it solidifies. In general, the more (i.e. larger volume of) bubbles that can be created and retained in the slurry during the foam hydration step, the lighter or lower the mass density will be for the final cleaner product. For detergent products with extremely low mass density, the two-number volume of the foaming slurry (or low-density foam) should thus be at least 150 percent, and preferably at least 200 percent (volume) of the non-foaming volume of the slurry, i.e. of the volume of the slurry before it is transferred into the foam state .

It should be noted that in the foregoing discussion of the foam hydration step in processes according to the invention, a better foam can be made, and consequently generally a more uniform final detergent product (especially when the invention is utilized as a continuous detergent process), if at least an effective amount of a "foaming agent" in the slurry at the time when the slurry is transferred to the foam state. "foaming agent" is intended to include synthetic organic anionic, nonionic and even ampholytic active detergent materials which are generally compatible with the alkali metal polyphosphates both in solutions and slurries of the commonly used detergent compositions. Thus, the term foaming agent includes, for example, such individual cleansing active ingredients as the well-known water-soluble soaps (ie sodium and/or potassium salts of fatty acids of coconut oil, oil fatty acids etc); water-soluble alkylarylsulfonates having from 6 to 20 carbon atoms, and preferably from 9 to 17 carbon atoms in their alkyl chains, such as sodium dodecylbenzenesulfonate and potassium tetradecylbenzenesulfonate; water-soluble alkyl sulfates, such as those made by sulfating aliphatic alcohols having from 6 to 20 carbon atoms in their branched or unbranched alkyl chains, typically comprising sodium and potassium lauryl (Ci2) sulfate, sodium and potassium hexadecyl sulfate, sodium and potassium octadecyl sulfate, etc.; as well as alkali metal salts of sulfated ethylene oxide and/or propylene oxide condensation products prepared by ethoxylation and/or propoxylation (and subsequent sulfation) of various organic hydrophobic compounds containing active hydrogen such as alcohols, mercaptans, phenols and amines; sodium and potassium alkyl glyceryl ethers, such as those derived from tallow and coconut oil, including e.g. sodium coconut oil fatty acid monoglyceride sulfate etc; fatty alkylolamides such as N-dodecylmonoethanolamide, N-octadecyldiethanolamide etc.; alcohol alkylene oxide condensates (ie alcohols with from 8 to 20 carbon atoms in either straight or branched chain configurations with from 6 to 30 moles of ethylene oxide and/or propylene oxide per mole of alcohol in their molecules); alkylphenol-alkylene oxide condensates (ie those made by condensation of alkylphenol, with an alkyl group containing from 6 to 20 carbon atoms in the chain) with from 6 to 30 or more moles of ethylene oxide and/or propylene oxide per mol alkylphenol) etc. 1. Among these, the substances in the anion class are preferred, while the fatty alcohol (or alkanol) sulphates with from 8 to 20 carbon atoms in their carbon chains are further preferred in processes according to the invention. Sometimes, if non-ionic detergents are used in the absence of a significant amount of one of the anionic detergents in the preparation of detergent products according to the invention, unexpectedly high viscosities are developed at one stage of the mixing process. It has been found that this problem can be alleviated by adding the "hydratable" polyphosphate last or almost last, and very slowly (ie over 2 minutes or more) while mixing in the other detergent ingredients.

The term "foaming agent" also includes substances which, when added to the slurry, contribute to some extent to the holding capacity or toughness or stability of the bubbles in the foaming slurry. Such substances (which are different from the well-known cleaning active ingredients of the kind described above) include polymers which are water-soluble sufficiently to contribute to the stability of the foam such as sodium carboxymethyl cellulose; sodium hydroxyethyl cellulose; polyvinyl pyrrolidone; hydrolyzed and partially hydrolyzed polymers made by reaction between a lower alkylene such as ethylene, propylene and methyl vinyl ether and maleic or fumaric anhydride, e.g. ethylene maleic anhydride, propylene fumaric anhydride, methyl vinyl ether maleic anhydride; polyvinyl alcohol etc. 1.

The amount of foaming agent in the slurries during the foam hydration step according to the invention can be varied considerably. In general, more than 0.1 percent by weight should be used in relation to the weight of the finished slurry, if you want finished detergent products with relatively low mass weights. But in order to achieve very low mass weights in the finished detergent products made with these methods, at least 0.25 and preferably 0.5 weight percent of the foaming agent should generally be used. Since different foaming agents act with different degrees of effectiveness, depending on many factors such as the temperature of the slurry, its concentration of "solids", the actually present constituents and many others, it is not possible to specify optimum here with certainty concentrations for each foaming agent. However, it is assumed that people with knowledge of the industry can determine the optimal concentrations for the manufacture of their own cleaning agent products from this description.

Practically any method of treatment may be used in carrying out the present invention to complete the various steps or stages of the processes described above. It is e.g. not critical in the order in which the various ingredients are added in the preparation of any slurry, except those which may contain more than a few percent by weight of alkali metal trimetaphosphate. Even where alkali metal trimetaphosphates are used in these processes, no other precautions are normally necessary to obtain excellent results than that compositions containing tripolyphosphate should not generally be mixed with the strongest bases, such as sodium hydroxide, unless the base is diluted with water to below 50% by weight, and preferably below 35% by weight, before mixing the strong base with the alkali metal trimeta phosphate. Otherwise, the strong base should be effectively diluted with water in the slurry itself as soon as possible after the base has been added. But if a manufacturer is not particularly interested in completely bringing the breakdown of the tripolyphosphate to a minimum during production, then this precaution need not be strictly followed either. If this precaution is followed, then there is an advantageous method which combines several of the unexpected desirable advantages which come with the use of alkali metal trimetaphosphate, and particularly sodium trimetaphosphate. This involves first preparing a practically completely composed slurry, which generally contains any foaming agent, anti-deposition agent, optical whitening agents, bleaching agents, fabric softeners, alkali metal silicate or fluorosilicate corrosion inhibitors, or other substances that one wishes to have in the finished cleaning agent composition or product, but which does not contain the strong base (here called the "prestage slurry"). This preliminary slurry must then also contain the trimetaphosphate. Due to the unexpectedly low viscosity of slurries containing trimetaphosphate, precursor slurries have relatively little water (compared to common detergent slurries which practically invariably contain hydrating or hydrated tripolyphosphate) such slurries can be made which retain their pumpability and other fluid characteristics. One can e.g. produce and use in processes according to the invention preliminary slurries that contain as much as 90% by weight non-volatile matter ("solids") which also include the trimetaphosphate. As long as the strong base is kept out of the preliminary slurry, its low viscosity can be maintained almost indefinitely, practically without any decomposition of the trimetaphosphate occurring. A detergent manufacturer can thus prepare his preliminary slurries well in advance of the time when he wants to make the final detergent product, if he so wishes. Moreover, if part of the manufacturing equipment were to be destroyed, a detergent manufacturer could store his preliminary slurry for long periods if necessary, practically without adverse consequences, but if he had made a regular slurry with sodium tripolyphosphate, then hydrolytic degradation of the tripolyphosphate could in the slurry during prolonged storage practically destroy the usefulness of the slurry for his processes.

When the preliminary slurry has been made, the cleaning agent manufacturer can then make use of several methods in the final and decisive step of the processes according to the invention. Since it is desirable that the foam hydration step is carried out relatively quickly, and since the conversion rate of trimetaphosphate to tripolyphosphate is very high at elevated temperatures, the preliminary slurry can be heated to a temperature above 50° and preferably above 70° C in one of the preferred designs of the invention before the strong base is mixed in. In this case, the conversion reaction proceeds rapidly

(usually within 2 minutes if e.g. used

sodium hydroxide or potassium hydroxide at the higher temperatures of the preliminary slurry) after the strong base is mixed into or with the preliminary slurry. Indeed, the heat of conversion of trimetaphosphate to tripolyphosphate, and thence to hydrated tripolyphosphate, is generally high enough that the conversion reaction may become autocatalytic in nature if most of this heat is not intentionally removed from the slurry. If e.g. a preliminary slurry which contains more than 10% by weight of sodium trimetaphosphate and has a temperature of 80° C, is quickly mixed with approx. 2 mol of sodium hydroxide per moles of trimetaphosphate under practically adiabatic conditions, then the conversion reaction begins immediately. The heat of conversion produces a temperature rise in the reaction mass, which in turn causes an increase in the conversion rate of trimetaphosphate to tripolyphosphate. Increases in conversion rate of ten times or more can be achieved by raising the temperature of the reaction mass by 25°C.

Thus, by mixing a strong base with the preliminary slurry at a relatively high temperature, the manufacturer can have reasonable safety

so that the foam hydration step will not need

excessively long time. Provided that the heat does not

removed from the system, may actually steam and foam

are usually produced in cleaning agent slurries which have been treated as described above

front (pre-stage slurry minus strong base)

within a few minutes from the time the strong base is mixed with the warm preliminary slurry. Practically equivalent results can also be obtained by mixing the preliminary slurry and the strong base with each other, or even

assemble the slurry in any way desired, at a relatively low temperature

(ie below 50° C) and then raise the temperature in the slurry to above 70° C, e.g. with externally supplied heat. This can be done by passing the slurry through or over an electric or steam heated heat exchanger.

Another way in which a manufacturer can achieve the same result is to send the relatively cool, fully composed slurry (containing both trimetaphosphate and the strong base) through a pipe surrounded by steam, using pressures above atmospheric and temperatures above 105° C if desired, to obtain even higher conversion rates. Before the conversion is finished, it is generally preferred that the slurry is deposited in or on some container so that the aforementioned foam hydration step can be completed without any particular degree of stirring. (Too much agitation during these processes where the "debinding" of the detergent slurries occurs can result in a considerable increase in the mass density of the final detergent product, compared to a product that has not been significantly agitated during the later part of the foam hydration step). Thus, if the foaming hydration step is carried out in a vessel containing a paddle or stirring blade or other device for internally stirring the slurry, then it is best that this stirring device is stopped while the foaming slurry solidifies. Or, if desired, the slurry can be discharged into a pan or other container, or onto a moving belt from the vessel with internal stirring shortly before the frothy slurry solidifies to reduce movement during this "settling" period. The strong base should be carefully and evenly distributed throughout the slurry before the solidification stage is reached.

Yet another convenient way to make low density cleaners via the preliminary slurry method described above is to run the process continuously. For example the warm preliminary slurry can be measured into a normal mixing vessel where this can be quickly and thoroughly mixed with the strong base which is also measured down into the device at a speed which is calculated to give the desired finished product. Then the fully assembled slurry can be poured or dropped or pumped from the mixing vessel onto or into a container where it is allowed to either begin or continue to foam and then solidify into the final detergent product.

Cold precursor slurry can be metered through an electrically or steam-heated tube or series of tubes before it is introduced into the mixer. If such a process is used continuously, it is convenient and advantageous to pour the fully composed slurry onto a moving belt arranged to receive liquid material. The slurry can then foam and steam on the belt, and then solidify on it. Then the low specific gravity product can be passed through a drying oven (usually operated at a temperature where the hydrated tripolyphosphate does not excessively decompose) if desired, to remove some of the excess free water that may be present. However, treatment in the drying oven is not decisive for a successful implementation of the invention. Or the hot fully composed slurry may be held in a pipe or line or other vessel under pressure higher than atmospheric, if desired, until the temperature of the slurry reaches the boiling point of the water it contains. Then it can be showered or sprinkled out in a tall tower like a normal spray drying tower and let through the tower. The tower may contain hot, dry air to help remove some of the free water, but the temperature in the tower should generally be kept significantly lower than those used in normal spray drying operations. Thus, foaming, hydration, and solidification during the fall through the tower can result in the formation of a low bulk density detergent product via a mechanism quite different from that typically used in similar equipment (ie, a spray drying tower).

In the following examples, which illustrate some designs of the invention, all parts are parts by weight unless otherwise stated.

Example 1 :

2000 parts water, 900 parts sodium dodecylbenzene sulphonate, 600 parts sodium lauryl sulphate, 1000 parts sodium sulphate, 2840 parts sodium trimetaphosphate are filled into a standard stainless steel mixing vessel with ordinary blade stirrers and fitted with a jacket so that cold or hot water or steam can be used in the jacket , 1140 parts sodium silicate (47% solids) with a SiO 2 /Na 2 O ratio of 2.40 and 55 parts sodium carboxymethyl cellulose of the type for cleaning agents. The resulting preliminary slurry is stirred for approx. 10 minutes, during which time the temperature is raised to 80° C by circulating steam through the jacket. Into the warm preliminary slurry which is stirred at moderate speed, 1590 parts of a 50% aqueous solution of sodium hydroxide is then rapidly poured. After approx. 45 seconds of moderate stirring, as the sodium hydroxide mixes well with the preliminary slurry, the temperature of the slurry begins to rise. The stirring is stopped just before the temperature of the slurry reaches 100° C. When its temperature reaches approx. 105° C, the slurry begins to expand and rise in the vessel, so that the volume of the foaming slurry is at least 2-8 times that of the preliminary slurry. Steam begins to escape from the bubbling mass, and it quickly hardens into a particulate, apparently wet, soft mass. After a few minutes, no more steam is formed from the solidified reaction mass, and the volume decreases slightly as it cools to room temperature. At this stage it contains approx. 30% water by weight, of which approx. 12.7% can be considered free water, and approx. 92% of the theoretical equivalent (based on the amount of sodium trimetaphosphate added to the preliminary slurry) of sodium tripolyphosphate, which is substantially present as hexahydrate. After air-drying overnight to remove most of the excess free water, the final detergent product is free-flowing, non-caking, substantially non-hydroscopic, has a bulk density of about 0.35, and contains approx. 54% by weight sodium tripolyphosphate hexahydrate. It should be noted that in example 1 one does not encounter any difficulty at all with regard to lumps either in the preliminary stage or the fully composed slurries. If one had followed the same procedure for preparing the slurry with anhydrous sodium tripolyphosphate instead of sodium trimetaphosphate, many troublesome lumps of undissolved, partially hydrated tripolyphosphate would probably have formed, especially if the high-temperature modification had been used, and these lumps are generally not desired by cleaners - intermediate producers neither in their slurries nor in their finished products.

Another surprising result that can be achieved by carrying out the processes according to the invention is that finished cleaning agent products made via such a method as shown in example 1 above give essentially clear aqueous solutions, even when dissolved in water in amounts of 0.5 to 1.0% by weight. In comparison, common heat-dried (usually spray-dried) detergent products invariably produce cloudy aqueous solutions. Data in Table 2 aptly demonstrate this:

Example 2:

A preliminary slurry is made similar to that produced in example 1, except that 3100 parts of a physical mixture of approx.

50% by weight of sodium trimetaphosphate and 50% by weight of anhydrous sodium tripolyphosphate of high temperature crystalline modification instead of the sodium trimetaphosphate. After the temperature in the preliminary stage has been raised to approx. 90° C, 1160 parts of a 35% by weight aqueous solution of sodium hydroxide are mixed rapidly within 30 seconds into the preliminary slurry. The mixture is then stopped and the slurry is allowed to foam. As soon as the volume of the foaming slurry is about five times that of the preliminary slurry, the foaming slurry is emptied from the mixing vessel in an approx. 10 cm thick layer, approx. 60 cm wide, on a walking ribbon. The reaction mixture on the belt solidifies quickly into a soft, particulate mass which, after passing through a tumbling rotary dryer, where dry air of 100° C is sent in countercurrent through the sprinkling

solid particles in approx. 10 minutes, provides an excellent free-flowing, non-caking, particulate detergent product that can be easily packaged and sold directly to the consuming public. Its mass density is about 0.45.

Example 3:

A similar preliminary slurry is made as in example 1 above. Its temperature is approx. 45° C. This is continuously measured into a stainless steel wire with an internal diameter of approx. 2.54 cm. Cables for approx. 9.12 meter length surrounded by a jacket for steam under pressure so the preliminary slurry can be heated to near boiling point. The warm preliminary slurry is fed together with a 50% by weight aqueous solution of sodium hydroxide which is measured into a mixing nozzle in an amount corresponding to 2.01 mol NaOH per moles of sodium trimetaphosphate in the preliminary slurry. The mixing nozzle has a stirrer and several guide vanes which are distributed and designed to provide rapid and intimate mixing of the preliminary slurry with the strong base. The temperature in the formed slurry is raised to approx. 115° C at the heat of reaction, and the pressure is increased to approx. 1.76 kg/cm<2>. From the open end of the mixing nozzle, the slurry is discharged onto a traveling belt, where steam is quickly formed and the product foams, and solidifies into a soft, spongy substance. After air drying, the final detergent product has a mass density of approx. 0.65. The cooled spongy material can be easily ground up into a free-flowing, granular product or sized for laundry detergents.

The methods according to the invention can benefit cleaning agent manufacturers in many ways, some of which have been mentioned before. In addition, it is a very valuable advantage that manufacturers can now make use of a "hydratable" polyphosphate in just one physical form for the production of many shapes and types of products. For example the finished detergent products with a relatively low mass density can be sent through a press machine, and then ground into a product with a higher mass density if desired. One can also regulate the density of the finished detergent products by using a small amount of a common antifoam agent in the slurry during the foam hydration step. In general, the more anti-foam agent that is used (such as the well-known silicones), the higher the mass density of the finished product. In addition to this, one can prepare a cleaning agent product with practically any desired composition (provided that it also contains a significant amount of one of the desired hydrated polyphosphates), by simply changing the types and amounts of ingredients in the precursor and /or fully assembled slurries as described above. Manufacturers of ta-bleached or shaped cleaning products can also benefit from this invention. For example some common detergent tablets are physically destroyed if exposed to a very humid atmosphere for more than a few hours, apparently because they initially contain anhydrous sodium tripolyphosphate which will increase in volume when it hydrates to hexahydrate on contact with the humid atmosphere. In comparison, tablets prepared from a finished detergent product such as that prepared in Example 1 will remain physically stable for weeks or more, even if exposed to high humidity and relatively high temperatures.

It is still an advantage of the present invention that it can be used for the production of shaped solid detergent products with a relatively low mass which contain a network of air spaces or cells. This cellular structure together with the fully formed shape (eg in the form of a bar of soap or practically any other shape) can be achieved by a precisely controlled release of steam during the foam hydration step of the processes according to the invention. It is important in the manufacture of such solid, cellular, shaped products that the entire amount of steam generated should be regulated so that very little, if any, of the steam bubbles out of the frothy slurry. In general, when producing one of these shaped solid preparations, one will control or regulate the reaction rate and/or the concentration of alkali metal trimetaphosphate and other "hydratable" polyphosphate materials in the slurry, so that the total amount of steam and or other gas is no more than approx. four times the total air-free volume of the fully assembled slurry (ie the frothy slurry is preferably less than 5 times the volume of the degassed one). If one of the more effective foaming agents is present in the slurry, the volume of the foaming slurry can be increased to approx. 8 or even 10 times the volume of the slurry without any particular breakdown of the flow of gas bubbles within the foam before it solidifies, (which breakdown and excess evolution of steam or gas from the slurry at or near the time the slurry solidifies can cause the final pro -the duct takes on particle form, which is generally not desired when producing shaped solid products with internal cell structures).

Perhaps the best way to carry out the above-mentioned regulation of the total amount of gas formed in the slurry is to handle it so that the desired gas volume is all that is formed in it, and that this gas is first developed during the later part of the foaming process. the hydration step. For example if slurries containing between 10 and 60% by weight of sodium trimetaphosphate are used in these processes, at least approx. half of the sodium trimetaphosphate is converted into tripolyphosphate without any significant amount of gas or steam being formed in the slurry. Then, during the foam hydration step, only enough gas should be injected or formed in the slurry to increase the volume of the foaming slurry as previously mentioned. It will be understood from the foregoing that since the release of large quantities of gas from the foaming slurry is not desired in this particular form of the invention, the majority of the free water that is originally present in the slurry should be removed or bound by hydration of the polyphosphate and other hydratable substances in the composition, such as sodium sulphate, sodium silicate and the like. It is generally preferred that at least 50% by weight of the free water is bound as hydrate of the polyphosphate. This limitation of the amount of gas formed in the slurry can, e.g. is carried out by mixing the strong base and the trimetaphosphate at a relatively low temperature, so that a large part of the heat of conversion from trimetaphosphate to tripolyphosphate can be used to raise the temperature of the slurry to the boiling point of the water it contains, or to the point where some other gas formed in it. Some of the heat can also be removed from the slurry using suitably placed heat exchangers.

Another method that can be effectively used to produce shaped, solid detergent products with low bulk weights is to pass a pre-composed slurry through a hot line, under pressure if necessary, to prevent gas evolution during most of the hydration time of the polyphosphate. When there is only a part of the hydration to be carried out, which part is sufficient to form approximately the desired amount of foam in the slurry, the slurry is poured into a mold or container. At this point, the temperature is generally at or above the temperature when gas is formed in the slurry. The continued hydration (and conversion if the tri-metaphosphate reaction is used) causes outgassing in the slurry, and also that it finally solidifies into the desired cellular product. If during these processes such conditions are used that no gas is formed in the slurry, the proper amount of gas can be injected into it in any desired manner shortly before the time when it solidifies, as outlined above.

It is easily realized from the foregoing that practically all materials that can be used in ordinary processes for the production of cleaning agent compositions can be used in processes according to the invention. It is also important that the invention need not be limited to working with slurries that contain all the ingredients that are usually found in ordinary heat-dried cleaning agent compositions. If alkali carbonate is used as a strong base in some of the processes according to the invention, the resulting finished products may contain several percent alkali metal bicarbonate in addition to the hydrated polyphosphate salt. And if an excess of alkali metal carbonate is used, this can appear in the finished detergent product either as the carbonate or its hydrate, depending on the particular process conditions used. Furthermore, the processes described here can be used for the production of practically pure sodium tripolyphosphate hexahydrate with a low mass, in addition to many mixed hydrated polyphosphate compositions which in turn can be used as raw materials in ordinary processes for the production of cleaning agent products.

Claims (3)

1. Method for producing a cleaning agent preparation containing a water soluble alkali metal polyphosphate hydrate, by producing a dispersion of a condensed phosphate starting material in water in the presence of a foaming agent, and the dispersion is brought to a foamed state, characterized in that a condensed phosphate starting material comprising alkali metal trimetaphosphate is dispersed in water, the dispersion also contains at least approx. half of the stoichiometric amount of a strong base required to convert the alkali metal trimetaphosphate, preferably sodium trimetaphosphate, to tripolyphosphate and at least 5 moles of water per moles of said trimetaphosphate and said dispersion are kept in a foamed state at a temperature in the range of 50 to 135° C, preferably 80 to 120° C, during which said trimetaphosphate reacts with said base and said water so that a hydrated tripolyphosphate and the reaction mixture hardens to a slightly porous solid. 2. Method as stated in claim 1, characterized in that the total amount of phosphate starting material in the dispensation is at least 10 percent by weight of the total solids in the sludge. 3. Method as stated in claims 1-2, characterized in that the dispensation from the beginning contains at least 10 percent by weight of sodium trimetaphosphate and at least 0.5 percent by weight of sodium sulfate.